1. Field of the Invention
This invention relates to a sheet conveying apparatus using a conveyance belt and a recording apparatus incorporating this sheet conveying apparatus and, more particularly, to a sheet conveying apparatus for electrostatically attracting and conveying a recording medium on which images are recorded with recording head in an ink-jet recording apparatus.
2. Description of Related Art
Generally, an ink-jet recording apparatus effects recording by discharging ink onto a recording medium such as paper or a synthetic resin and has advantages such as the recording head can be easily made compact, high resolution images can be recorded with high speed, the running cost can be made inexpensive, the apparatus creates low noise because of its non-impact nature, and color images can be easily recorded using multicolor inks. Particularly, a full-line type apparatus using a line type recording head having multiple orifices arranged in a width direction of the recording medium can record at a higher speed.
With a full-line type apparatus, however, because a distance between a recording head located at the most upstream position and a recording head located at the most downstream position becomes longer, the recording medium may float at the recording area, thereby irregularly forming the recording images, as well as possibly causing paper jamming or the like. Therefore, it is required to pull the recording medium downward so that the recording medium does not float. A method has been known in which conductive electrodes as urging means are provided, to which electric charges are applied to generate electrostatic force, thereby adhering the recording medium made of dielectric material.
In such an ink-jet recording apparatus, the recording medium fed by a feeding apparatus is held to a top surface of the conveyance belt by means of the electrostatic adhering or attracting means formed in the conveyance belt in a recording area for the recording head, and the recording medium is conveyed by the conveyance belt while being recorded by the recording head.
Referring to FIG. 11 to FIG. 14, an example of a conventional ink-jet recording apparatus is described. In FIG. 11, the recording sheet P as a recording medium is stacked on a feeding section 51 and fed sheet by sheet from the topmost sheet by a feeding roller 52.
The recording sheet P thus fed is adhered on a conveyance belt 56 having an adhering force generating means 55 as described below by a driven roller 53 and a pinch roller 54, and is conveyed to a recording starting position on a platen 58 by a conveyance belt 56 conveyed by a drive roller 57 driven by a pulse motor as a drive source.
The conveyance belt 56 is tensioned with the drive roller 57, the driven roller 53, and a pressure roller 59; one end of the pressure roller 59 is rotatively formed on the other end of an arm 60 formed in a rocking manner to the platen 58; and the arm 60 applies a tension to the conveyance belt 56 as it is pushed by a spring 61.
Numeral 62 is a full-line type recording head in which plural recording elements are arrayed across the whole width of the recording area of the recording sheet P. The recording heads 62 are placed with a prescribed interval in the order of 62K (black), 62C (cyan), 62M (magenta), and 62Y (yellow) and are mounted to a head holder 63.
FIG. 13 is a plan view of an adhering or attracting force generating means 55 viewed from the top side. In FIG. 13, the adhering force generating means 55 formed at the conveyance belt 56 is constituted of comb shaped electrode plates 64 and ground plates 65 made of a conductive metal in which respective teeth are independent from each other, and are disposed alternatingly in a direction perpendicular to the moving direction of the conveyance belt 56 as well as across the recording area of the recording heads 62.
Voltage receiving portions 64a, 65a exposing patterns at each edge with respect to the moving direction of the conveyance belt 56 are connected to the electrode plates 64 and the ground plates 65, and as shown in FIG. 12, voltage supplying brushes 66, 67 serving as voltage supplying means capable of contacting the voltage receiving portions 64a, 65a are provided over the voltage receiving portions 64a, 65a, and positive and negative voltages are fed to the electrode plates 64 via the voltage receiving portion 64a in contact with the voltage supplying brush 66, and the ground voltage is fed to the ground plates 65 via the voltage receiving portion 65a in contact with the voltage supplying brush 67.
FIG. 14 is a cross-section taken along section line XIVxe2x80x94XIV shown in FIG. 13 and shows a cross-section of the adhering force generating means 55 formed on the conveyance belt 56. As shown in FIG. 14, the adhering force generating means 55 is protected as the electrode plates 64 and the ground plates 65 are sandwiched by a base layer 56a and a surface layer 56b constituted of a synthetic resin such as polyethylene, polycarbonate, or the like.
With the above structure, the recording sheets P are attracted to an upper surface of the conveyance belt 56 by the attraction force generating means 55 and conveyed by the conveyance belt 56 while being recorded by the recording heads 62.
Numeral 68 is a cleaning roller pair for removing stains attached to the conveyance belt 56 and is provided in pressured contact with the conveyance belt 56. Numeral 69 is a delivery roller and is driven by rotative force of the drive roller 57 via a transmission means (not shown). Numeral 70 is a spur for pressing the delivery roller 69, and the recording sheet P after recording is nipped by the delivery roller 69 and the spur 70 and delivered to a delivery tray 71 to be contained. The spur 70 has a shape with sharp points such that the recorded image ink is not transferred because the spur 70 runs rotatively on the recording surface after recording.
However, according to the above prior art, because the voltage is fed by the voltage supplying brushes 66, 67 where the attraction force generating means 55 made of the comb shaped electrodes constituted of the electrode plates 64 and the ground plates 65 is provided on the conveyance belt 56 and where the voltage receiving portions 64a, 65a are formed as exposed externally on both sides with respect to the conveyance direction of the conveyance belt 56, inks unexpectedly discharged out of the recording heads 62, misted ink droplets (ink mist) made of satellites, micro dots, and the like caused by spraying inks, dusts, paper dusts, and so on may be easily attached to the voltage receiving portions 64a, 65a and the voltage supplying brushes 66, 67, and in such a situation, contact between the voltage receiving portions 64a, 65a and the voltage supplying brushes 66, 67 becomes unstable, thereby precluding supply of the feeding voltage.
It has been devised that a protection member be provided around the voltage supplying means to isolate it from external portions, but the proposed protection member does not have a structure such that the entire periphery of the conveyance belt is covered thereby, so that substantially the same problems as the above art may arise, such as inks and dusts being attached to the exposed voltage supplying portions.
This invention intends to solve the above problems. It is an object of the invention to provide a sheet conveying apparatus and a recording apparatus having this sheet conveying apparatus capable of protecting the entire voltage receiving portions from inks unexpectedly discharged out of the recording heads, misted ink droplets (ink mist) made of satellites, micro dots, and the like caused by spraying inks, dusts, paper dusts, and so on by covering the entire edges of a conveyance belt formed with the voltage receiving portions by a protection member in a manner so as to isolate these portions from the exterior, and of rendering stable contact between the voltage receiving portions and voltage supplying means to stabilize the supplying of voltage.
To accomplish the above object, a sheet conveying apparatus according to the invention includes attraction force generating means formed with electrodes for electrostatically adhering a sheet as a recording medium, a conveyance belt having voltage receiving portions to which a voltage is supplied at an edge or edges in a moving direction, and voltage supplying means for supplying a voltage to voltage receiving portions, and has a feature that the entire side edge or edges of the conveyance belt are covered by a protection member provided in contact with or placed adjacent to the conveyance belt so that the voltage receiving portions are isolated from the exterior with a prescribed interval at a periphery of the voltage receiving portion.
According to this structure, because the entire side edge or edges of the conveyance belt formed with the voltage receiving portions are covered by the protection member so as to be isolated from the exterior, the voltage receiving portions as a whole can be protected from inks unexpectedly discharged out of the recording heads, misted ink droplets (ink mist) made of satellites, micro dots, and the like caused by spraying inks, dusts, paper dusts, and so on, and stable voltage supply can be realized upon stable contact between the voltage receiving portions and voltage supplying means.
In such a sheet conveying apparatus, the attraction force generating means can be constituted of electrode plates and ground plates to which voltages different from one another are applied, wherein the electrode plates and the ground plates are arranged alternatingly; the voltage receiving portions of the electrode plates and the ground plates can be placed on the opposite edges of the conveyance belt with respect to the moving direction of the conveyance belt; and the protection member can be formed on each edge of the conveyance belt with respect to the moving direction of the conveyance belt for protecting the attracting force generating means.
Alternatively, in such a sheet conveying apparatus, the attracting force generating means can be constituted of electrode plates and ground plates to which voltages different from one another are applied; the electrode plates and the ground plates can be arranged alternatingly, wherein the voltage receiving portions of the electrode plates and the ground plates are placed on one edge of the conveyance belt with respect to the moving direction of the conveyance belt; and the protection member can be formed on the one edge of the conveyance belt at which the voltage receiving portions are placed with respect to the moving direction of the conveyance belt for protecting the attracting force generating means.
The attracting force generating means can be constituted of the electrode plates and the ground plates, which are in a strip shape, arranged alternatingly and in a comb shape such that their lengths run in a direction perpendicular to the moving direction of the conveyance belt.
The sheet conveying apparatus may have a structure with a sealing member attached to the protection member for sealing a space between the protection member and the conveyance belt by contacting an upper surface of the conveyance belt. According to this sheet conveying apparatus, this sealing member surely isolates the voltage receiving portions of the attracting force generating means from the exterior.
With such a sheet adhering conveying apparatus, where the voltage supplying means is supported by a part of the protection member, the apparatus can be free from adverse influence of inks from the recording means and dusts and can be formed with a reduced number of parts and reduced costs, because the voltage supplying means is also isolated from the exterior by the protection member.
The protection member may have a support for supporting the conveyance belt at a position facing the voltage supplying means through the conveyance belt, thereby surely contacting the voltage supplying means to the voltage receiving portion of the conveying means. It is also preferable that the support of the protection member is formed in a convex shape and that friction reducing means is provided between the support and the conveyance belt.
The sheet conveying apparatus may have a cleaning member for cleaning, in contact with the conveyance belt, the voltage receiving portion of the adhering force generating means on an upstream side of the voltage supplying means in the moving direction of the conveyance belt. With such a structure, the voltage receiving portions of the adhering force generating means are always cleaned in association with movement of the conveyance belt before contacting the voltage supplying means, so that both can be surely contacted. The protection member also serves as a bracket of the cleaning member, so that the number of parts and the costs can be reduced.
In the sheet adhering conveying apparatus thus described, the protection member may separably contact the conveyance belt. Particularly, where the protection member is attached to a jamming treatment door openable or detachable during paper jamming treatments of a jammed sheet, the protection member is contacted with and separated from the conveyance belt in association with movement of the jamming treatment door. The protection member, which would otherwise be an obstacle to maintenance on the conveyance belt, can be moved according to opening of the jamming treatment door, so that the conveying apparatus can afford ease of operation in jamming recovery.
In the sheet conveying apparatus, the conveyance belt can be wound around at least a drive roller and a driven roller and tensioned by at least one pressure roller.
In another aspect, a recording apparatus according to the invention includes a sheet conveying apparatus having: a conveyance belt for supporting and conveying a sheet; attracting force generating means formed in the conveyance belt having electrodes for electrostatically attracting the sheet; voltage supplying means for supplying a voltage to a voltage receiving portion as a part of an electrode of the attracting force generating means formed at a side edge with respect to a moving direction of the conveyance belt; and a protection member formed at a side edge with respect to the moving direction of the conveyance belt for isolating the voltage receiving portion in the electrode of the attracting force generating means from an exterior by covering the entire side edge of the conveyance belt in contact with or placed adjacent to the conveyance belt, and recording means arranged at a position facing the conveyance belt.
The recording means may eject droplets of ink from an orifice to effect recording on the sheet. Furthermore, the recording means can be provided in plural number in the moving direction of the conveyance belt and be so arranged that the orifices are aligned in a direction perpendicular to the moving direction of the conveyance belt. The recording means may also be a full line type recording head in which plural recording elements are arranged across the entire width of a recording area of the sheet.
With such a recording apparatus, the recording means may discharge ink from the orifice utilizing film boiling occurring in the ink by thermal energy applied by an electrothermal converter.